“Why do they call it slip?” Pippin asked his great aunt as he watched her mix powdered clay with water to make what looked to him to be a thick, grey mud.

She shrugged as she stirred. “It’s what it’s ever been called,” she noted.

She indicated that the slip was at last ready to pour into the mould. Pippin lifted the great bowl and tipped it slowly. His hand trembled, the funnel fell, and liquid clay poured across the workbench and onto the floor. His aunt stepped forward to lend a hand—and landed flat on her back.